A tube-and-fitting assembly--such as a bicycle frame, playground equipment frame, tool stand, or the like--typically has a plurality of fittings normally cast of some rigid material and connected to the ends of the tubes. In the oldest arrangement as used particularly in a bicycle frame, the tube ends were simply brazed or welded to the fittings.
Recently, however, systems such as described in French patent documents Nos. 2,432,425 and 2,441,531 are employed where the fittings have pointed pins that are fitted into the ends of the tubes. Such an arrangement requires that a special flaring mandrel be provided to shape the tube ends complementary to the pins. In addition to ensure an accurate fit it is necessary to provide a complex jig for assembling the bicycle frame so that the various elements are put together in the right orientation.
Thus the prior system is relatively complex, necessitating careful preparation of each tube end and the use of a substantial piece of assembly equipment. As a result fabrication costs are elevated.